The present invention refers to a method for bit stream decoding. The bit stream comprises a number of consecutive samples.
Furthermore, the invention refers to a computer program, which is able to run on a computer, in particular on a microprocessor.
Further, the invention refers to a bit stream decoding unit for decoding a bit stream. The bit stream comprises a number of consecutive samples.
Finally, the present invention refers to one of a number of nodes of a communication system. The nodes are connected to a communication media for transmitting data among the nodes. The data is transmitted across the communication media in the form of a bit stream, whereas the bit stream comprises a number of consecutive samples.
Various types of communication systems are known in the art. Generally, they comprise a communication media, which for example is a data bus. Various nodes are connected to the communication media. Each node comprises a host controller, a communication controller, a bus driver and optionally a bus guardian. Data can be transmitted across the communication system according to various protocols. An example of such a protocol is TTCAN (Time Triggered Controller Area Network) for time triggered communication systems.
Data transmission can be effected in communication cycles, which comprise various time slots assigned to the nodes of the communication system. Each node can send data across the communication media within the timeslot assigned to the node. Which timeslots are assigned to which nodes is part of a communication media access scheme. If a node wants to transmit data, the data is brought into a format specified in the protocol used. Formatting the data is effected by the communication controller of the node. The formatted data is called bit stream. The bit stream is forwarded from the communication controller to the bus driver, which translates the formatted data into electrical signals which then are applied to the communication media within the timeslots assigned to the node.
A node receiving information receives the electrical signals from the communication media. The signals are transformed into the respective bit stream in the bus driver of the node. From there the bit stream is forwarded to the communication controller, where the bit stream has to be decoded.
Decoding of the bit stream is conducted in the physical layer of the communication system. The decoding comprises in particular extracting logical frames and symbol information, and passing this information to a protocol engine of the node. In particular the following steps have to be performed during decoding of the bit stream:                Detecting bit edges between two bit cells within the bit stream applied to the bit stream decoding unit at an input from the communication media, and        Determining the actual value of a bit cell within the bit stream.        
Depending on the detected edges between two bit cells, in particular depending on the detected initial edge of the first bit cell within the bit stream, the decoding within the communication controller is started and data reception is activated. The communication controller itself runs on a time triggered basis, however the processing of the bits runs event triggered. Therefore, it is very important to reliably determine the initial edge of the bit cell within the bit stream. Otherwise the communication controller is started to no purpose.
It is an object of the present invention to provide a possibility of fast and in particular reliable decoding of a bit stream.